Suitable cable to make extension lead

Rotor

Hi , i have bought a piece of garden machinery with a powerful 3kw electric motor. The manufacturer states prominently 'do not use an extension lead' and research seems to advise that this is because of voltage drop and that a way to reduce this problem is to use 2.5 square mm cable (assuming the distance isn't great - say 25 mts)

So, is this advice correct and if so what grade of cable. I've managed to confuse myself with the many different codes - 3183A, 3183Y and various BS standards

Is this suitable?

http://www.ebay.co.uk/itm/371482203448?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Risteard

Firstly it is likely that the manufacturer is stating not to use an extension lead because it is liable to melt (not because of voltage drop) if not fully uncoiled.

Secondly, it is never appropriate to fit 2.5mm^2 cable to a BS1363 plug. To do so does not comply with BS1363 - the maximum cable size is 1.5mm^2.

Larger sizes have to be used with BS EN 60309 Commando plugs and sockets.

wellused

What flex would be used for a 3kw electric fire for instance?

discat11

1.5 mm is perfectly suitable for up to 16a load so easily able to handle 3kw.
For electrical heating items use the heat resistant coated stuff.

http://www.rospa.com/home-safety/uk/northern-ireland/electricity/flexes-cables/flexes/

You'd have to be hundreds of meters away on an extension lead to see any voltage drop at all even on a multimeter.

Wig

What piece of garden machinery is it?

How about asking the manufacturer why they say not to use an extension flex? Does the machine not come with an extension flex already?

Rotor

Wig wrote: »

What piece of garden machinery is it?

How about asking the manufacturer why they say not to use an extension flex? Does the machine not come with an extension flex already?

It's a log splitter and it comes with 10m 1.5mm lead but because I've got 4 tons of wood to split I would far rather take Mohammed to the mountain rather than vice versa, and 25m should do that.

The advice i got was 'longer or narrower lead =Volt drop = more current= more heat= shorter life' but he was no electrician which is why I posted here to check.

Ectophile

discat11 wrote: »

You'd have to be hundreds of meters away on an extension lead to see any voltage drop at all even on a multimeter.

That seems a bit unlikely. Using figures from CSE Cables http://www.csecables.com/technical-tables-useful-info/voltage-drop-calculations/ you're looking at a drop of 29mV per amp per metre for 1.5 sq.mm cable. Over 100 metres at 13A, that would be 0.029 x 100 x 13 = 37V drop. The result at the far end would be well outside the acceptable range.

Rotor

Ectophile wrote: »

That seems a bit unlikely. Using figures from CSE Cables http://www.csecables.com/technical-tables-useful-info/voltage-drop-calculations/ you're looking at a drop of 29mV per amp per metre for 1.5 sq.mm cable. Over 100 metres at 13A, that would be 0.029 x 100 x 13 = 37V drop. The result at the far end would be well outside the acceptable range.

Thanks ectophile, so looking at that table for a 25 mtr cable at 1.5mm it would be a drop of 9.43v (over and above any existing drop)whereas a 2.5mm cable would be 5.85v. Is that correct? If so is either figure enough to be concerned about?

zax47

Do you mean 25 more metres or 25 metres total?

Quick bit of maths tells me that 3kW load on 230V at 25m (10m + 15m) using 1.5mm is fine for voltage drop (just 4.1% which is below the allowable 5%) but at 35m total length (10m+25m) you'd need to up it to 2.5mm to stay under 5% drop.

So, yes IMO you can add a 15m extension using 1.5 no problem, but any longer you'd need 2.5mm. Me, I'd use some 2.5mm "Multiflex" anyway if it's gonna be outside and rolled up & generally mucked about.(yes, it will just fit in a "normal" BS1363 13A plug, but I'd use proper commando connectors & make up a small patch cable to a "normal" plug.)

https://www.tlc-direct.co.uk/Main_Index/Cable_Index/Multi-Flex/index.html

https://www.tlc-direct.co.uk/Main_Index/Plugs_and_Sockets_Industrial_Index/MK_Commando/index.html

Rotor

Well that's put the cat among the pigeons. I was plugging it into a socket in an old barn so the log store is circa. 25m from this. However, the mains supply comes into the house and this is then distributed to the barn which is about 50m away (i.e. the supply has already traveled 50m before getting to the plug I was going to put the extension cable into)

I think I need to find someone with a voltage tester to see where I am.

The choices are run an extension cable from the house (40m x 2.5mm + 10m x 1.5mm the machine already has) or see what voltage I get at the barn and see what leeway i've got.

I see 5% drop is considered acceptable : any idea how quickly problems/damage/decreased lifespan accrue as that figure is exceeded? ( I know it can only be a guess)

Scrounger

Rotor wrote: »

Is this suitable?

http://www.ebay.co.uk/itm/371482203448?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Yes, and probably OK run from the barn too (can't be 100% sure as we don't know all the details about this particular circuit ratings).

Although UK mains is specified at 230V it is in real life 240V (RMS) so that allows an additional 10V for any voltage drop.

I would try (much cheaper) 30m 13A extension reel first as it should be able to cope (providing it is fully unwound whilst in use). :beer:

Scrounger